Ejector

ABSTRACT

A nozzle ( 41 ) is made of a sintered metal, and a pressure increasing portion (a mixing portion ( 42 ) and a diffuser ( 43 )) is manufactured by plastic-forming a metal pipe. Accordingly, the nozzle ( 41 ) can be manufactured in a short time while high accuracy in machining is maintained. Thus, the cost of manufacturing an ejector ( 40 ) can be reduced.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional Application of U.S. patent applicationSer. No. 10/435,786 filed on May 12, 2003. This application claims thebenefit of JP 2002-136954, filed May 13, 2002. The disclosures of theabove applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ejector, that is a kinetic pump fortransferring a fluid by entrainment with a working fluid discharged athigh speed, and that is effectively applied to a refrigerator(hereinafter an “ejector cycle”) in which the ejector is adopted as pumpmeans to circulate a refrigerant.

2. Description of the Related Art

A nozzle of an ejector accelerates a working fluid by decompressing theworking fluid. Accordingly, the shape of the inner wall of the nozzlethat is in contact with the working fluid requires a high accuracy inmachining, i.e., a high accuracy in dimension and a predeterminedsurface roughness.

In the ejector for an ejector cycle, a speed energy is converted to apressure energy during mixing of a refrigerant injected from the nozzleand a refrigerant sucked from an evaporator in a pressure increasingportion. Accordingly, similar to the shape of the inner wall of thenozzle, the shape of the inner wall of the pressure increasing portionrequires a high accuracy in machining.

Therefore, conventionally, the nozzle is manufactured by electricaldischarge machining or wire cut electric spark machining and thepressure increasing portion is manufactured by cutting. However, in theelectrical discharge machining, the wire cut electric spark machiningand the cutting, it is difficult to reduce the number of man-hours,i.e., the time of machining and, therefore, it is difficult to reducethe cost of manufacturing of the ejector.

SUMMARY OF THE INVENTION

In view of the above problems, the first object of the present inventionis to provide a new ejector different from a conventional one, and thesecond object is to reduce the cost of manufacturing of the ejector.

In order to archive above objects, according to a first aspect of thepresent invention, there is provided an ejector, which is a kinetic pumpfor transferring a fluid by entrainment of a working fluid dischargedfrom a nozzle (41) at high speed, wherein the nozzle (41) is sintered athigh temperature after compression-molding fine particles.

Accordingly, the nozzle (41) can be manufactured in a short time while ahigh accuracy in machining is maintained. Thus, a new ejector differentfrom a conventional one can be obtained, and the cost of manufacturingof the ejector can be reduced.

According to a second aspect, the nozzle (41) is made of a metal.

According to a third aspect, the nozzle (41) is sintered after beingcompression-molded so that the filling rate of the fine particles is notless than 96%.

Thus, the nozzle (41) can be prevented from being damaged due tocavitation because the hardness of the nozzle (41) is improved.

According to a fourth aspect, there is provided an ejector, which is akinetic pump for transferring a fluid by entrainment of a working fluiddischarged from a nozzle (41) at high speed, wherein the nozzle (41) issintered at high temperature after compression-molding metal powders,and has an inner surface on which a film of nickel is formed.

Accordingly, the nozzle (41) can be manufactured in a short time while ahigh accuracy in machining is maintained. Thus, a new ejector differentfrom a conventional one can be obtained, and the cost of manufacturingof the ejector can be reduced.

Also, the nozzle (41) can be prevented from being damaged due tocavitation because the hardness of the inner surface covered with a filmof nickel is improved.

According to a fifth aspect, there is provided an ejector being appliedto a vapor-compression refrigerator which has a radiator for radiating arefrigerant having high temperature and pressure that is compressed by acompressor (10) and an evaporator (30) for evaporating a decompressedrefrigerant having low temperature and pressure and transmits heat froma low temperature side to a high temperature side, comprising a nozzle(41) for decompressing and expanding the refrigerant by converting apressure energy of the refrigerant, which emitted from the radiator(20), to a speed energy; and pressure increasing portions (42, 43) forincreasing the pressure of the refrigerant by converting a pressureenergy to a speed energy while mixing the refrigerant injected from thenozzle (41) and the refrigerant sucked from the evaporator (30), whereinthe pressure increasing portions (42, 43) are manufactured by deforminga pipe by plastic forming.

Accordingly, the pressure increasing portion can be manufactured in ashort time while a high accuracy in machining is maintained. Thus, a newejector different from a conventional one can be obtained, and the costof manufacturing of the ejector can be reduced.

According to a sixth aspect, the pressure increasing portions (42, 43)are manufactured by deforming a pipe by swaging.

According to a seventh aspect, the pressure increasing portions (42, 43)are manufactured by deforming a pipe by press working.

According to an eighth aspect, the pressure increasing portions (42, 43)are manufactured by deforming a pipe by spinning.

The numerical reference attached in parentheses to the component namesdescribed above are given to show an example of correspondence tospecific components of embodiments to be described later.

The present invention may be more fully understood from the descriptionof preferred embodiments of the invention set forth below, together withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic view of a first embodiment of an ejector cycleaccording to the present invention;

FIG. 2 is a schematic view of a first embodiment of an ejector accordingto the present invention;

FIG. 3 is a p-h diagram;

FIG. 4 is a schematic view of a manufacturing method of a pressureincreasing portion according to a first aspect of the present invention;and

FIG. 5 is a graph of a filling rate and a wear rate of a nozzle.

DESCRIPTION OF PREFERRED EMBODIMENTS

A first embodiment of the present invention will be described below. Inthe present embodiment, an ejector according to the present invention isapplied to an ejector cycle for a vehicle air conditioner. FIG. 1 is aschematic view of an ejector cycle 1 using freon (134 a) or carbondioxide as a refrigerant. FIG. 2 is a schematic view of an ejector 40.FIG. 3 is a p-h diagram showing macroscopic operations of the entiretyof the ejector cycle.

A compressor 10 is a known variable-capacitance compressor that sucksand compresses a refrigerant by the power obtained from an engine formoving a vehicle. A radiator 20 is a high pressure side heat-exchangerthat carries out a heat-exchange between the refrigerant discharged fromthe compressor 10 and outside air so as to cool the refrigerant.

An evaporator 30 is a low pressure side heat-exchanger that carries outa heat-exchange between air flowing into the room and a liquid-phaserefrigerant so as to evaporate the liquid-phase refrigerant to cool airflown into the room.

The ejector 40 decompresses the refrigerant to expand the same so as tosuck a gas-phase refrigerant evaporated in the evaporator 30, andconverts an expansion energy to a pressure energy so as to increase theinlet pressure of the compressor 10.

As shown in FIG. 2, the ejector 40 is composed of a nozzle 41 thatconverts a pressure energy of refrigerant to a speed energy, toisentropically decompress and expand the refrigerant; a mixing portion42 that mixes the gas-phase refrigerant evaporated in the evaporator 30and the refrigerant injected from the nozzle 41 while sucking thegas-phase refrigerant by the refrigerant injected from the nozzle 41 athigh speed; a diffuser 43 that converts a speed energy to a pressureenergy to pressurize the refrigerant while mixing the refrigerantinjected from the nozzle 41 and the refrigerant sucked from theevaporator 30; and the like.

In the mixing portion 42, a driving flow and a suction flow of therefrigerant are mixed so that the sum of the kinetic momentum of thedriving flow and the kinetic momentum of the sucking flow is conserved.Accordingly, the pressure (static pressure) of refrigerant is increasedeven in the mixing portion 42.

In the diffuser 43, the cross-sectional area of a passage thereof isgradually increased to convert a speed energy (dynamic pressure) ofrefrigerant to a pressure energy (static pressure). Accordingly, in theejector 40, the pressure of refrigerant is increased in the mixingportion 42 and diffuser 43. Therefore, the mixing portion 42 and thediffuser 43 are collectively called a pressure increasing portion.

In the present embodiment, in order to accelerate the speed ofrefrigerant discharged from the nozzle 41 to the speed of sound or more,a Laval nozzle having a throat portion 41 a at which the sectional areaof a passage of the nozzle becomes smallest, is adopted. However, as amatter of course, a convergent nozzle may be adopted.

In FIG. 1, a gas-liquid separator 50 is gas-liquid separating means intowhich the refrigerant discharged from the ejector 40 flows and whichseparates the refrigerant into a gas-phase refrigerant and aliquid-phase refrigerant and stores the refrigerants. A gas-phaserefrigerant outlet port and a liquid-phase refrigerant outlet port ofthe gas-liquid separator 50 are connected to the suction side of thecompressor 10 and the inflow side of the evaporator 30, respectively. Athrottle 60 is a decompressing means for decompressing the liquid-phaserefrigerant discharged from the gas-liquid separator 50.

In the present embodiment, as shown in FIG. 3, a high-pressurerefrigerant flowing into the nozzle 41 is pressurized to the criticalpressure of the refrigerant or more in the compressor 10. Referencenumerals indicated with black dots in FIG. 3 show the state of therefrigerant at positions indicated by the reference numerals with blackdots in FIG. 1.

Operations of the ejector cycle will be briefly described below (seeFIG. 3).

The refrigerant discharged from the compressor 10 is circulated towardthe radiator 20. Thus, the refrigerant cooled in the radiator 20 isisentropically decompressed and expanded in the nozzle 41 of the ejector40 and, then flows into the mixing portion 42 at the speed of sound ormore.

The refrigerant evaporated in the evaporator 30 is sucked into themixing portion 42 by a pumping operation associated with entrainment ofthe high-speed refrigerant flowing in the mixing portion 42.Accordingly, the low pressure side refrigerant is circulated through anarrangement of the gas-liquid separator 50, the throttle 60, theevaporator 30 and the ejector 40 (pressure increasing portion).

While the refrigerant (suction flow) sucked from the evaporator 30 andthe refrigerant (driving flow) injected from the nozzle 41 are mixed inthe mixing portion 42, the dynamic pressure of the refrigerant isconverted to the static pressure of the refrigerant in the diffuser 43.After that, the refrigerant is returned to the gas-liquid separator 50.

A manufacturing method of the ejector 40 and features thereof will bedescribed below.

1. Manufacturing Method of the Nozzle 41

In the present embodiment, the nozzle 41 is made of a sintered metal,i.e., metal (e.g., stainless steel) powder is charged into a die tocompression-mold the nozzle 41 and, then, the nozzle is sintered at hightemperature and pressure. The hardness of the nozzle 41 is improved bysetting the filling rate of the metal powder into the die at 96% ormore.

Normally, the filling rate of a sintered metal is set at about 80%. Ifthe nozzle 41 is manufactured at a filling rate of 80%, the hardness islow and, therefore, there is a high possibility that the portion of thenozzle 41 subsequent to the throat portion 41 a may be damaged due tocavitation occurred in the throat portion 41 a. However, in the presentembodiment, the portion of the nozzle 41 subsequent to the throatportion 41 a can be prevented from being damaged due to cavitation(corroding) because the filling rate is set at 96% or more.

Therefore, the cost of manufacturing the ejector 40 can be reducedbecause the nozzle 41 can be manufactured in a short time while a highaccuracy in machining is maintained.

2. Manufacturing Method of the Pressure Increasing Portion

In the present embodiment, as shown in FIG. 4, a pipe made of a metal(e.g., stainless steel) is deformed by plastic forming, to manufacturethe pressure increasing portion.

A plastic forming method is, for example, swaging, press working,spinning and the like (see Japanese Industrial Standard B 0122).

Therefore, the cost of manufacturing of the ejector 40 can be reducedbecause the nozzle 41 can be manufactured in a short time while a highaccuracy in machining is maintained.

A second embodiment will be described below. In the first embodiment,the filling rate of metal powder into the die is set at 96% or more, toimprove the hardness of the nozzle 41. However, in the presentembodiment, the inner surface of the nozzle 41 is coated with a nickelfilm by plating, to improve the hardness of the nozzle 41.

FIG. 5 is a graph showing a relation between a filling rate and a wearrate. As is clear from FIG. 5, if the inner surface of the nozzle 41,i.e., the portion of the nozzle 41 which is in contact with therefrigerant, is coated with about 10 to 15 μm of nickel plating, thesame hardness of the nozzle 41, as that at a filling rate of 96%, can beobtained even if the filling rate is set at about 80%.

Another embodiment will be described below. In the above-describedembodiment, the nozzle 41 is made by sintering metal powder. However,the present invention is not limited thereto. The nozzle may be made bysintering, for example, ceramic powder.

In the second embodiment, the nickel film is formed on the inner surfaceof the nozzle 41. However, the material of the film is not limited tonickel.

While the invention has been described by reference to specificembodiments chosen for purposes of illustration, it should be apparentthat numerous modifications could be made thereto by those skilled inthe art without departing from the basic concept and scope of theinvention.

1. An ejector being applied to a vapor-compression refrigerator whichhas a radiator for radiating a refrigerant having high temperature andpressure that is compressed by a compressor and an evaporator forevaporating a decompressed refrigerant having low temperature andpressure and transmits heat from a low temperature side to a hightemperature side, a nozzle for decompressing and expanding therefrigerant by converting a pressure energy of the refrigerant, which isemitted from the radiator, to a speed energy; and pressure increasingportions for increasing the pressure of the refrigerant by converting aspeed energy to a pressure energy while mixing the refrigerant injectedfrom the nozzle and the refrigerant sucked from the evaporator, whereinthe pressure increasing portions are manufactured by deforming a pipe byplastic forming.
 2. An ejector according to claim 1, wherein thepressure increasing portions are manufactured by deforming a pipe byswaging.
 3. An ejector according to claim 1, wherein the pressureincreasing portions are manufactured by deforming a pipe by pressworking.
 4. An ejector according to claim 1, wherein the pressureincreasing portions are manufactured by deforming a pipe by spinning.